Heavy Organic Growth - Need Help!

I am currently in the process of building a 12v portable softwash system on a cart. It will be using a 5gpm pump at 70 psi. I plan on using Apple Wash as the surfactant, I also have EBC (unsure if anyone uses that in a roof mix).

I have been approached to clean a concrete tiled roof as he wants it clean for painting. From my research on here and on YT, the consensus is that if there is heavy organic growth present on the roof, you simply leave it to fall off with the wind and the rain after treating it with your roof mix.

My question is that if there is heavy organic growth (picture below is from the rental I currently live in, lots of lichen present) on this concrete tiled job, he will expect it all gone once I have left as presumably he won’t want to wait 6-12 months for the lichen to fall off in its own time before painting it. What suggestions do you have to turn a roof like the one pictured into one that is clean and free of heavy lichen?

Personally I think its unrealistic given the type of growth present and the amount to expect all traces of it to be gone from the roof once I’m finished.

I think the only way is to either 1) use low pressure to try and rinse it off or 2) use a broom to brush it off. As its a concrete tiled roof, I don’t think it would be a great idea to be walking on it as tiles could be damaged.

I would love to hear any suggestions or tips on removing heavy lichen growth.

I can’t answer the main question, but I did find this if it helps any. That pitch may be problematic however.

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Thanks for that mate, I haven’t seen the job yet so don’t know the pitch. He will be sending me pics later on today.

Need some photos bud, it’s like describing a haircut to a barber over the phone.


@MuscleMyHustle That was well said
I’m going to use that one


that’s nothing like the photo above, I was thinking corn growing on the roof. Mix up some 4-5% and go to town, with the heat you guys are getting over there at the moment it will start flaking in 10 minutes, let the sh bake on good and give it a nice rinse. Be sensible with pressure.

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Yeah I know, I was using that as an example for my question of removing heavy lichen growth. Plus its always good to get advice on removing it from roofs that have heaps of it on them. I’ve seen a lot around my area that are like the one I live in.

Once I get all my bits, I’ll treat my one and see how well it goes.

If you’ve got big clumps of growth like on yours, you probably want to brush off the bigger clumps before you treat or I’ve been known to use my shooter tip to knock off clumps, just make sure to not shoot it under the tile. On one like yours, that’s bad, after you brush off bigger clumps, pre-wet, let sit for about 5 min before you apply solution. It softens it up and makes more absorbant before you apply solution.


Thanks for the information Racer!

I hoped 4% would be enough. Maybe 2 applications. Nope. I had to walk the roof and rinse with jrod on a lance to get the roof clean.

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I would have gone 50/50 and walked away

What happened to the concrete? Lots of stripes going on there.

We are talking about the roof. You already know what I would do to the driveway

I haven’t done any roofs yet but I’m pretty sure if your customer wants a tile roof clean for painting, then it isn’t enough to soft wash it. You’ll need to pressure clean the whole thing. Take a surface cleaner up there or get one of the specifically made for roof cleaning accessories.

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Yeah I was thinking that too tbh

I would treat with 4-6% then rinse with enough pressure as needed to remove remaining debris, youre going to have to walk it as are the painters just don’t stomp around like a drunk elephant.
Take pictures of any broken tiles you notice prior to clean- usually will be a couple and if you break any yourself be honest about it and tell the client- some have spares in the shed or are ok with a sikaflex repair.


Don’t take any surface cleaner up there.


Why not? If you are tied off, I don’t see the problem. Many people do it.

What is the deal with the specialized roof cleaning SC? wouldn’t that still risk forcing water under the tiles?